The present invention relates to image forming systems and processes, particularly to such a system for reproducing color images by scanning an original and using computer directed signals to control an ink-spray head, and more particularly to an improved image forming system and process using a drive roller assembly and deflection prevention means, a plurality of adjustable spray heads, and/or apparatus for forming images on opposite sides of a recording medium.
Over the years various systems and processes have been utilized for reproducing color images. Substantial effort has been directed to systems for making enlarged prints, such as for billboards. In such prior systems an original image is scanned to produce control signals that operate the reproduction equipment. The image to be reproduced is placed on a conventional scanner and the image is scanned in a conventional manner, with the signals from the scanner being modified by a computer to achieve the desired effects (e.g. color) with the particular deposition medium (e.g. ink) being used. These signals control the movement and operation of the spray head and the speed of movement of a substrate or recording medium on which the image is to be formed.
U.S. Pat. No. 4,914,522 issued Apr. 3, 1990 to P. L. Duffield et al exemplifies the prior imaging systems and discusses early efforts for reproducing enlarged prints or images, such as used for outdoor advertising, artistic representations, and other purposes, which are produced on sheets of recording medium, such as paper or vinyl, while being transported from a supply-roll to a take-up roll. Thus, very long and/or wide images can be produced. This patent employs the use of separate ink and air supply jets whereby a flow of air, supplied at a constant pressure, is turned on and off in accordance with the control signals and passes across an ink meniscus formed on the tip of an ink jet or nozzle, causing the ink to be sprayed onto the recording medium.
U.S. Pat. No. 4,839,666 issued Jun. 13, 1989 to W. Jayne involves an image forming system in which controlled amounts of a deposition medium, such as ink, are sprayed from an orifice for deposition on a surface. This is accomplished by using a pneumatically driven image forming system capable of supplying a precisely control led volume of the deposition medium through a spray head, having coaxial air and deposition medium nozzles, which forms a siphon feed means drawing a controlled amount of the deposition medium from within the spray head through an orifice in the spray head.
U.S. Pat. No. 5,144,328 issued Sep. 1, 1992 to D. Blake et al is directed to a method for producing a large scale color graphic that presents substantially the same spectral content to a viewer when the graphic is illuminated with front or back lighting. This is accomplished by applying a color film on a first surface and a second color film on a second surface such that the color films create the desired colored graphic image and are produced in registry with one another. The color films may be formed on opposite sides of a sheet-like substrate so as to define mirror images of each other, or the first color film formed on one surface of the substrate and the second color film formed on one surface of a translucent substrate which is positioned over the first color film such that the translucent substrate is between the color films and the color films are in registry to produce a resultant desired color forming image.
While the prior art imaging systems and processes have provided the capability to produce enlarged colored images in various sizes and colors, the imaging process is slow and thus costly. For example, with prior known imaging systems, each pass of the printer assembly across the recording medium or substrate produces a very narrow hand (about 0.1-0.2 inch) of the image, thus requiring numerous passes of the printer assembly. Thus, there is a need in this art for a system and/or process by which the imaging speed can be increased. Also, there is a need in the art, particularly for large imaging systems, of a means to prevent/reduce/eliminate deflection of the recording medium due to its width, whereby the image can be formed thereon without the need of compensation. In addition, there is a need for a more economical way of producing large scale colored images that involve illumination with both front and back lighting.
The above-mentioned needs in the large scale imaging systems are satisfied by the apparatus and process of the present invention. The speed of imaging is increased by using a plurality of adjustably controlled spray heads by which a larger strip of the image is deposited on the recording medium at each pass across the medium, thus reducing the number of passes. The deflection problem is solved by an improved roller type support mechanism for the recording medium, and which allows the recording medium to be easily replaced without substantial down time of the imaging system. The imaging for front and back lighting is accomplished a modification of the existing systems and processes to enable the formation of mirror images on opposite sides of the recording medium and/or the use of special translucent and/or transparent coatings. Thus, the present invention enables the production of large color images while reducing the time and associated costs involved in the imaging operation.